This invention relates to the recovery of energy from geothermal brines and other hot water sources, and is particularly concerned with a process and system of the aforementioned type, employing direct contact heat exchange between the hot brine or hot water feed, and a working fluid, the process being operated and the system designed to achieve maximum throughput (mass flow rate) of hot brine or hot water feed, maximum efficiency and minimum scale deposition, with minimum diameter of the heat exchange column, and consequently approximate minimum cost.
Direct contact heat exchange (DCHE) has been proposed as a method for recovering thermal energy from scale depositing geothermal fluids, e.g. hot geothermal brine. Thus, U.S. Pat. No. 3,988,895 to Sheinbaum discloses power generation from hot brines by passing a hot fluid containing salt such as geothermal brine, in direct contact heat exchange relation with a working fluid such as isobutane.
In the copending application Ser. No. 589,068, filed June 23, 1975, by Samuel G. Woinsky, there is described a process and system for recovery of energy from geothermal brine and other hot water sources, which comprises cooling the brine or hot water source in direct contact heat exchange relation with a working fluid in a direct contact heat transfer column, and having as an important feature the operation of the heat transfer column at or above the critical pressure of the working fluid.
In the copending application Ser. No. 611,310, filed June 23, 1975, by Samuel G. Woinsky, there is described a similar process and system as in the above mentioned application, and having as an important feature operation of the heat transfer column at a pressure below the critical pressure of the working fluid.
In such direct contact countercurrent heat exchange processes and systems, as described in the above Sheinbaum patent and the above copending applications, in order to transfer heat more effectively for the purpose of utilizing thermal energy from the geothermal brine, the temperature differential between the brine and the working fluid, such as isobutane, should be minimized at each stage throughout the countercurrent heat exchange system. Further, in order to transfer a commercial quantity of heat from geothermal brines to the working fluid, a large volume of the fluids must be handled.
It is accordingly an object of the present invention to provide a process and system for direct contact countercurrent heat exchange between a hot water containing fluid such as geothermal brine, and an immiscible working fluid, so as to obtain maximum throughput, that is, mass flow rate, of such hot aqueous fluid in the column. Another object is to provide a process and system of the above type, and particularly utilizing a sieve plate heat exchange column, wherein the temperature differential between the hot water containing fluid such as brine, and the working fluid are reduced throughout the column, and the column efficiency increased. Still another object is to provide a process and system of the above type wherein lost work is minimized and efficiency maximized. A still further object is the provision of a direct contact heat exchange process and system as described above, wherein scale from hot aqueous liquids containing salts, e.g. geothermal brine, is minimized, while maximizing throughput of hot water containing fluid such as brine in the column.